A Cell Phone Manufacturer Has Been Experiencing Physical Quality Control

Multiple Choice

A cell phone manufacturer has been experiencing physical quality control problems. The back case of phones does not always fit and snap into place on the phone body. The dimensions of the case have constantly been in statistical process control (SPC) . To monitor process control, the company uses -charts. Seven samples, each containing three phone cases, were selected from different batches. The data is presented in Table 1 below.
Table 1: Cell Phone Plastic Case Widths in Centimeters Data*
$\begin{array} { | l | l | l | l | l | l | l | l | } \hline \text { Observation } & \text { Sample 1 } & \text { Sample 2 } & \text { Sample 3 } & \text { Sample 4 } & \text { Sample 5 } & \text { Sample 6 } & \text { Sample 7 } \\\hline 1 & 6.02 & 5.92 & 5.88 & 5.99 & 6.05 & 5.94 & 6.00 \\\hline 2 & 5.97 & 5.83 & 5.97 & 6.08 & 6.06 & 5.96 & 5.95 \\\hline 3 & 5.90 & 5.87 & 5.88 & 6.08 & 5.98 & 5.99 & 5.82 \\\hline \text { Average } & 5.963 & 5.873 & 5.912 & 6.051 & 6.035 & 5.963 & 5.923 \\\hline \text { Range } & 0.12 & 0.09 & 0.09 & 0.09 & 0.08 & 0.05 & 0.18 \\\hline\end{array}$
*The sample averages and ranges help avoid simple math errors and quicken the time to complete the SPC analysis.
If
for the
-chart is 1.023, the lower control limit for the
-chart (LCL) will be:

A) less than or equal to 3.0.
B) greater than 3.0 but less than or equal to 4.0.
C) greater than 4.0 but less than or equal to 5.0.
D) greater than 5.0.